Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


solder mask wrinkles

Carol Zhang

#8912

solder mask wrinkles | 19 October, 1999

Hi, I tried to use high temperature solder (540 - 570F)to connect four spacers on the board. The solder mask around the spacers wrinkled a lot.I can even see a few bulbs around it. I use hot plate and solder rings. After hot plate is heated to appropriate temperature, I put board on the plate. the bottom side of four spacers contact the plate. Then I put solder rings around the collar of spacers, wait them to melt and form joint. After soldered the spacers, the rest of components will be installed on the board and wave soldered. The wrinkle of the mask happened at the component side, not at the soldering side. Is there someone has any idea that whether this type of mask wrinkle is acceptable. Is there any spec. ? And probably, Dave's suggestion is right. I should use glue to hold these spacers. Any suggestions are welcome and thanks a lot for the help.

Carol

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Brian

#8913

Re: solder mask wrinkles | 19 October, 1999

Carol

You're asking a helluva lot if you heat a PCB to 300�C and probably more in such an uncontrolled process. I'm surprised it is not irreparably damaged or, at least, discoloured. I don't think any solder mask is designed for this temperature.

What's wrong with screw-in or riveted spacers?

Brian

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#8914

Re: solder mask wrinkles | 19 October, 1999

Hi Carol, does that happen also when you solder them with an iron ? That�s what I did with some joints using hightemp solderwire and couldn�t notice anything you mentioned. What Brian and Dave said should be worth considering.

good luck Wolfgang

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Carol Zhang

#8915

Re: solder mask wrinkles | 19 October, 1999

Hi, thank you for the idea. I may try solder iron, but it much more slower since I have to solder spacers one by one. a stimpson press is used to press the spacer on the board and the edges of the spacers are rolled. Then we solder the edges to make the connection stronger. I guess it is the rivet spacer Brain mentioned. Why we solder it after it is pressed on the board? because if we don't do thay, the spacers will rotate when we try to tight the board with bus bar in the following assembly. I have not dig it out thoroughly yet. I cannot figure out how a threaded spacer will work on the 0.062" thk board. do i need to put a nut on the other side? please give me some hints. thank you. carol

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#8916

Re: solder mask wrinkles | 19 October, 1999

Hi Carol You can use a threaded standoff and put a screw through the board and into the standoff with the screw from the buss bar coming into the other end of the standoff. You should use a SEMS type screw or a internal star type lockwasher with a plain screw. Another type (but more expensive) is the "jack screw" type of standoff as used on a D type connector to hold the plug in. This is a receptacle tyoe standoff for the screw from the buss bar with a screw projecting from the other end. It is used with a nut. John Thorup

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Jeff Sanchez

#8917

Re: solder mask wrinkles | 19 October, 1999

Carol, I think the guys are right about you stand off problem but I want to address the wrinkleing of your masking. Although I think the temps you are subjecting the board to are very high and more than likely creating problems of their own. I think you might be working with a poor masking finish as well? I have noticed these types of problems on boards that have tin under masking. Rather than bare copper under masking. You need to find out if this is so. Your desired finish should be "bare copper under mask". This is always a better board to work with. Can you see chipping on the masking? Is it shiny Tin under the cracks? If so, change it! Your boards will be more friendly to work with. This will not help with you stand off problem. But in the end always makes for a better board. ..........Just something I noticed, Jeff Sanchez

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